Objectives: Although cardiopulmonary resuscitation (CPR) skills decay after training, little is known about appropriate retraining methods. Our aim was to evaluate the effectiveness of a 1-minute self-retraining (with automated assessment and feedback) at 3 months after the initial 45-minute chest compression-only CPR training in a simulated randomized controlled trial.Methods: After the initial 45-minute chest compression-only CPR training, participants were randomly assigned to either a 1-minute self-retraining group or a control group. Three months after the initial training, the selfretraining group individually attended the 1-minute self-retraining with a self-training device. The participants' resuscitation skills were evaluated by a 2-minute case-based scenario test 6 months after the initial training. The primary outcome was the number of correct chest compressions with appropriate depth.Results: A total of 109 subjects participated in this study. With regard to the primary outcome, the number of chest compressions performed at the appropriate depth, there was not a statistically significant difference between groups (136. Conclusions: The 1-minute self-retraining program with hands-on practice appears to help preserve certain chest compression skills. Further efforts to provide methods to maintain CPR skills should be considered.A lthough early cardiopulmonary resuscitation (CPR) and shocks by bystanders are the keys to increase survival after sudden cardiac arrests, 1 the proportions of bystander CPR and automated external